Method of treating insulating sleeve



May 3, 1932. H. HALPERIN ET AL 1,856,415

METHOD OF TREATING INSULATING SLEEVES Filed Feb. 25, 1928 Patented May3, 193.2

erre rarer carica HERMAN- I-EAPERIN AND ALEXANDER P. THOMS, OF CHICAGO,LLINOIS METHOD or casarme rNsULATINe sLEEvE i Application filed February25, 1928. Serial No. 257,090.

This invention relates to insulating sleeves for use in the insulatingjoints of cable sheaths, and has to do more particularly with a methodof treating such sleeves to render l themy airand moisture tight.

It is essential that theinsulating joints of the cable sleeves beresistant to the action of the air and liquids, such as wat-er, weakacids,

, alkalies, and the various agencies that operate upon the cablesheaths, and that such joints be air and moisture tight. y

According, to our invention we provide as an article of manufacture an'insulating sleeve comprising a pair of light cylindrical thimbles .orferrules bonded to each other mechanically, but separated electrically7by a body of insulation formed in place. In the preferred embodiment ofour invention the body' ofjinsulation consists ofa ring of a iffsynthetic' resinous or phenol condensation product formed in place uponthe ends of two similar brass thimbl-es or ferrules. The manner ofsecuring a tight lit and an effec- HJ tive closure betweenthe'insulating material d and the metal of the ferrules is an importantfeature of our invention.

ln forming the insulating sleeve the two metal rings or ferrules areplaced in a suitable mold in spaced relation and the ring of 3insulating material employed is molded about the adjacent end portionsof the ferrules, the mold beingheated so as to rend-er the insulatingmaterial plastic and insure Close contact thereof with the metalferrules, also 0 facilitating the molding operation. During thisAmolding of the insulating material about the ferrul-es,fthe ferrulesand the insulating "material becomes unequally heated due to theimpossibility, from a practical standpoint, of uniformly heating thesections of the mold throughout the entire mass thereof', and the factthat the metal ferrules conduct the heat muchmore readily than theinsulating material. As the co-etlicient of expansion of the insulatingring is diderent from the co-eilicient of expansion of the metalferrules, when thesleeve is removed from the mold and cooled a slightspace may be left between the ring and the outer faces of the endportions of the ferrules imbedded therein. These spaces areobjectionable as being a possible source of leakage while also renderingthe mechanical construction of the sleeve imperfect. le have found thisobjection can be Y avoided by properly heating the sleeve, aftercompletion thereof, so as to raise the component parts of the sleeve tothe same temperatur-e, and then slowly coolinor the sleeve. This heatingof the sleeve is preferably conducted in a liquid of suitable characterto 6 effect a seal about the inner ends of the ferrules. An oleaginousmaterial, such as an oil or grease heated to a proper temperature topenetrate t-he spaces referred to, is preferably employed for thispurpose. Further 66 objects and advantages of our invention will appearfrom the detailed description.

ln order that those skilled in the art may more readily understand ourmethod, We have illustrated several forms of insulating sleeves 70constructed in accordance with our invention, though We do not limitourselves to these particular forms of sleeves as our invention can beapplied to advantage to sleeves of various types in which a metallicmember vor ferrule is used with an insulating member or ring formed ofsynthetic resin or a phenol condensation product or the like or otherinsulating material which is molded about a metal member.

ln the drawings:

Figure l is an elevation of an insulating sleeve constructed inaccordance with our invention; f

Figure 2 is a longitudinal sectional view 85 through the sleeve shown inFigure l;

Figure 3 is a sectional View through a modified form of the sleeve;

Figures is a sectional view through a second modified form of sleeve; 9U

lFigure 5 is a view illustrating diagrammatically the treatment of thesleeve in an oil bath.

ln the form of sleeve of Figures l and 2, tivo brass ferrules l aresecured together by an insulating ring Q, formed of a suitable phenolresinous product or the like. The inner end portions of the ferrules 1are preferably provided with spaced circumferential grooves so as to be,in efl'ect,'corrugated. The m outer faces of the ribs or corrugationsthus formed are preferably knurled vso as to obtain a better mechanicalconnection between the vferrules 1 and the ring 2.

y2 except that a metallic ring 4 is set into the outery periphery ofVthe insulatingl ring 2.

The several forms of sleeves illustrated and described are formed insuitable molds .consisting `of relatively large metal parts, these moldsbeing heated at the two ends and exposed tothe air on their sides. 'Inthese molds the insulating material is molded onto the brass ferrules ata temperature of approximately 3500 F. Usually about fourteenV minutes`is vrequired to moldthe sleeve which is thenremoved from themoldfandallowed to cool in therair. If desired, the sleeve 'when r-emoved fromthe mold can be placed `in a'suitablevoven and slowly cooledbypermitting cooling of the oven.r In` either case,l we have found thatthere is a possibility of leakage between'the insulating ring and thebrassferrules ortheysleeves due to unequal expansionpand contractionthereof, as

v previously pointed out. It is necessary to use, for theinsulatingring, armate'rial of` high dielectric strength. We have `found. thesynthetic resin known kas a phenol condensation productparticularlysuited for this purpose` as it is relativelyy non-hygroscopic, ab-

sorbsvery little moisture, possesses very ap- Y f preciable mechanicalstrength, and has a dielectric strength of the order to 200 volts permil in thickness. The ferrules are preferably of brass which has aco-efcient of expansion of approximately .000020 inches per degree riseCentigrade whereas the synthetic resin known as a phenolcondensationproduct such asproposed herein hasa coeiiicient ofapproximately .000025. By using these two Vmaterials we reduce thetendency for the Contact# ing surfacesofthe insulating material and iV,the brass 'rings to separate. While the sleeve constructed in thismanner is fluid tight under f pressure, invmany instances, we have foundthat a slight leakage between the ring and the ferrule can be detectedvat times.V This leakage can be detected by subjecting the sleeves to aproper test vsuch as closing the ends of the sleeve andl forcing airinto it under a pressure yof from to 60 lbs. per square inch. l Y' vItis essential, as above pointed out, that the vinsulating-sleeves beeffectively sealed againstleakage.v We have found that this can'be'accomplished by treating the sleeve,

after the same has been formed in the mold, in a suitable manner toraise the component parts of the sleeve to the same temperature and sealany slight spaces which may be present between the insulating ring andthe ends of the ferrules. In accordance with our invention, the sleeveissubjected to a heat treatment in a suitable oleaginous material, such asoil or grease, and is then cooled. In Figure 5 of the drawings we haveshown a suitable container 5 in whichk isV placedl a suitable quantityofAoil, this oil being heated by an electric plate 6, or othersuitableheat ing means, vbeneath the 'container 5. A suitable oil or grease isplaced in the container 5 and is heated to a temperature ofapproximately 275Ov F.` lVe have found that many materialsv can be` usedsuch as thin transformer oil, heavy cylinder oil, linseed oil, orgrease. VVThe sleeve is immersed in the hot bath of oil or grease whichis then allowed to cool, which usually takes about two hours7 thefsleeveremaininginthe bath during cooling thereof. yThe sleeve may be placed.in thebath after ithas been heated'to the proper temperature ofapproximately 275 F or it may be placed in the bath before heatingthereof, as desired. We have found that sleeves treated in this mannerwill not leak when filled with air at a pressure of lbs. per squareinch, or when subjected to a vacuum correspondingto about one millimeterof mercury in absolute pressure. v Many sleeves constructed and treatedin accordance with our inventionhavebeen installed and in active servicefor many months, and none of these have developed leaks; Other sleeveswhich have not been installed have been subj ected to pressure testsperiodically and have shown no signs of developing leaks so that sleevestreated in accordance with our method are rendered permanentlyy air 'andmoisture ti ht.

lu just what manner the heat treatment of the sleeve eects sealingthereof is not fully understood in all respects. When the sleeve isfirst formed in the mold' and has been cooled, the insulating materialdoes not have perfect contact with'the ferrules throughout theentirecircumference thereof, as previouslyrpointed out. It is thought` thatwhen the sleeves are heated in oil or other suitable oleaginousmaterial, in the manner described,v

the lcomponent parts of the sleeve are heated uniformly to the sametemperature. As the co-eiiicient of expansion of the insulating materialis slightly greater than the coefficient of expansion of brass, thesynthetic resin expands slightly more than the brass and allows a filmof oil or grease to 'enter between the ferrule and the insulating ring.It isalso vprobable that any imperfections in the inner surface of theinsulating material are filled with the oil or grease and it may be thatthe outer grooves, at least, of the ferrules are lull covered with afilm of oil or grease. Itis thought that these films are trapped as thesleeve cools and the insulating ring contracts about the ferrules, thusproviding a seal which renders the connection between the ring and theferrule air and water tight. rI`he operating temperatures of theinsulating sleeve in use would val'y between 85 F. and F. As thesleeveis subjected to a temperature of 275 F. during the treatmentthereof, the temperatures to which the sleeve is subjected under actualconditions of use will not affect nor in any way tend to destroy theseals about the ends of the ferrules. In experiments, the sleevestreated in this manner were alternately placed in cold water, and inboiling water, several times and then tested. The testgave no indicationof any decrease in the effectiveness of the seals between the ring andthe ferrules.

Articles which are molded from synthetic resins are open to theobjection that they warp out of shape. This is probably due tomechanical stresses imposed during molding of the article underpressure. We have found that this objection can be avoided by heattreating the molded article in a proper' manner to let down or relievethese internal stresses. In the specific embodiment of our inventionherein set forth, this heat treatment consists in heating the article ina fiuid bath at a temperature below the softening temperature of thesynthetic resin used and then cooling it. The particular temperatureemployed may vary, but we have found a temperature of approximate-ly 275F. well suited for this purpose. Our invention comprehends, in itsbroader aspect, heat treating an article molded of the synthetic resinknown as Bakelite and analogous materials, which we believe to bebroadly new.

While we have described our method as being applied specifically to asleeve comprising a ring formed of a synthetic resin and bra-ssferrules, it has been found equally effective in treating a sleevecomprising a synthetic resin molded on lead tubing. We do not,therefore, limit our invention to the specific combination of asynthetic resin and brass, since it is adapted for'use with structuresof various types in which phenol condensates and similar materials aremolded upon metal elements associated therewith..

What we claim is:

j l. The method of treating an article pressure molded from avcondensation 'product and completely cured, consisting in immersing thearticle in a fluid bath heated to a temperature below the softeningtemperature of the molded product but sufficiently high to relieve theinternal stresses of such article, and then cooling the article.

2. The method of rendering fluid tight during use the joint of anarticle formed of inseparably joined elements having differentcoefficients of expansions, one of which is formed of a condensationproduct, consisting in flowing sealing fluid which is immiscible inwater into spaces existing between said elements, then trappng saidfluid in said spaces 1 and maintaining the component parts of thearticle joined together during use of the article after treatment.

3. The method of'rendering fluid tight during use the joint in anarticle formed of inseparably oined elements having differentcoefficients of expansion, one of which is formed of a condensationproduct, consisting in heating the article, flowing a sealing fluidwhich is immiscible in water into spaces eX- isting between theelements, then cooling the article thereby contracting said elements andtrapping the fluid in said spaces and maintaining the component parts ofthe article joined together during use of the article after treatment.

4. The method of rendering fluid tight during use the joint in anarticle formed of a metal element and an element formed of acondensation product molded about said metal element and inseparablyjoined thereto, consisting in heating the article and thereby causingexpansion of said element, flowing a sealing fluid which is immisciblein water into spaces existing between the elements, then cooling thearticle thereby contracting the elements thereof and trapping the fluidin said spaces and maintaining the component elements of the articlejoined together during use of the article after treatment.

5. The method of forming an insulating sleeve of molde'd insulation andmetal and rendering the joint between the insulation and metal fluidtight during use which consists in first molding the insulating materialinseparably upon the metal and thereafter subjecting the sleeve of metalwith the insulating material inseparably molded thereon to treatment ina heated liquid immscible in water, depositing said liquid in spaces eX-isting between the insulation and the metal and then cooling the sleeveof insulation and metal.

6. The method of forming an insulating sleeve of molded insulation andmetal and and cooling the sleeve of insulation and lmetal.

7. The method of forming an insulating sleeve of molded insulation andmetal and rendering the joint between the insulation and metal fluidtight during use which con- Sists in molding the insulating materialinseparably upon the metal and thereafter m-V Inersng the sleeve ofmetal with the nsulating material nseparably molded thereon in a bath ofol heated to a temperature below Y thesoftenng temperature of the moldedin- Y sulaton and Causing seid oil to enter and he deposlted 1n spacesexlstlng'between the 1nsulaton yand metal, and then cooling the sleeveof insulation and metal.

InV Witness Whereof,we hereunto subscribe our names this 21st day ofFebruary, 1928.

HERMAN HALPERIN.

f ALEXANDER P. THOMS.

